Electrical connector with insulated ferrule



1953 F. J. SOWA ELECTRICAL CONNECTOR WITH INSULATED FERRULE OriginalFiled Oct. 28, 1944 2 Sheets-Sheet 1 'VIII .III

INVENTOR Dec. 2, 1958 F J, sow 2,863,132

ELECTRICAL CONNECTOR WITH INSULATED FERRULE Original Filed Oct. 28, 1944i 2 Sheets-Shet 2 INVENTOR FPA/VK (7f Sow/1. @512 f TTORNEYs,

asssnsz ELECTRICAL 'C'UNNECTQR WITH INSULATED Franit 5. owa, Cranford,N. 3., assignor to AMP Incorporated, a corporation of New Jersey Uri.@ctober 1x3 1944, Serial No. 560,785. ll)- ten and this appiicationOctober 1, 1951, Serial No. 254,515

1 Ciaim. (ill. 339-213) This invention relates to electrical connectorsand more particularly to electrical connectors having insulatedferrules.

I It is an object of' this invention to provide an inexpensive connectorhaving the ferrule portion thereof for engaging a conductor and holdingit in good conducting re lation to a terminal portion, but fullyinsulated against peripheral contacts. Another object of the inventionis to provide an electrical connector having a metallic ferrule and aninsulated sleeve thereon capable of crimping by the usual methods toform a mechanically secure and electrically good connection with a wireor other conductor onto which the terminal is applied.

Although in this specification and the accompanying drawings I amshowing and describing a particular example and various modificationsthereof, it should be understood that these are not intended to beexhaustive or limiting of the invention, but on the contrary are chosenand presented for purposes of illustration and in order to explain theprinciples of the invention and the practical employment of thoseprinciples in applying the invention to practical use, and thus to sofully instruct others skilled in this art that they will be enabledreadily to modify and to select and substitute alternatives, each as maybe best suited to the particular conditions of any given application oruse.

in the accompanying drawings,

Figure 1 is a view in axial section of a terminal connector embodyingthe invention;

Figure 2 is a cross-sectional view of the same terminal connector takenon line 2-2 of Figure 1;

Figure 3 is a view in axial section of a similar connector crimped ontoan insulated wire;

Figure 4 is a view partly in axial section and partly in side elevationof another terminal connector embodying the invention;

Figure 5 is an isometric view of the connector of Figure 1 after itsapplication to a wire and crimping in the same manner as the ferruleshown in Figure 3; and

Figure 6 is an isometric view showing the connector of Figure 1 inprocess of being crimped to the form shown in Figure 5.

Referring to these drawings the reference character 10 identifies anelectrical terminal of conventional form. This may be made, for example,from flat strip of annealed high conductivity pure copper stamped out toform the tongue portion as shown with the hole 11 for reception of abinding post, and a substantially rectangular portion which is rolled upas shown to cylindrical form bringing the ends together at 13 as shownin Figures 1 and 2.

A seamless sleeve 15 is formed, e. g. by extrusion, of plasticinsulating material of the type which can be expanded under conditionssuch that it retains so-called elastic memory, i. e. tends more or lessslowly to return to a form and dimensions approaching that from which ithas been expanded or deformed. Such return is gen erally delayed orinhibited by cold and hastened by heat. There are many such plasticsknown to the trade, mostly ice compositions of organic polymers withplasticizers. I have found particularly suitable for such use anextruded tubing manufactured from a plasticized copolymer of vinylchloride and vinyl acetate. This material, at ordinary atmospherictemperature and when dry and relaxed, should be tough and resistant todeformation, although it is capable of molding at higher temperatures;moreover it can be stretched mechanically or swollen in solvents orotherwise deformed without heat so as to retain a tendency to return tothe form which it had before such expansion or deformation; and thisproperty I take advantage of according to my present invention, first tofacilitate the assembly of the parts, and secondly to permit crimping ofthe insulated ferrule by ordinary crimping tools without destruction ofthe insulating sleeve.

Referring once more to Figure 1, it Will be noticed that the interiordiameter of the free end of the sleeve 15 is smaller than the exteriordiameter of the ferrule 12. This relationship is purposely chosen sothat after the sleeve has been expanded and fitted over the ferrule theelastic recovery will grip the ferrule with a relatively highconstrictive pressure with the consequences: first, that the seam 13,where the ends of the ferrule portion are abutted together, is sealedand closed against the entry of corrosive influences; secondly, thattheends of the sleeve are drawn in over the end of the ferrule givingmore complete insulation and holding the sleeve securely in its desiredlongitudinal position; and thirdly, that the ferrule is held againstspringing open under the influence of the crimping tool.

Before this small sleeve can be fitted onto the ferrule it is, ofcourse, necessary that it be in some way enlarged. According to mypresent invention this may be done either by swelling in solvents or bystretching mechanically.

If the sleeve is to be swollen by means of solvents, it is convenient.to keep a supply of the sleeves immersed in the solvent until ready foruse, then to remove them as needed and place each over a ferrule;whereupon evaporation of the solvent causes elastic recovery with theresult that the sleeve securely grips the ferrule and is drawn over itsedges as shown in Figure 1.

Unless special precautions are taken, however, this soaking in solventwill result in a leaching out of the plasticizer from the plasticmaterial to such extent that after it is shrunk onto the ferrule ittends to become so brittle that a subsequent attempt to crimp theconnector onto a wire, may destroy the sleeve. 1 have found that thisdiificulty can be avoided by using for this swelling operation either aliquid which swells the plastic but is a nonsolvent for the plasticizer,or it may be a solvent of the plasticizer but having already dissolvedin it sufficient plasticizer to assure a desired concentration ofplasticizer in the sleeve after soaking in the solution. This latter isof particular advantage because it gives a full control of plasticizerconcentration independent of the composition of which the sleeves mayhave been originally formed. Thus it is ordinarily an advantage to havemore plasticizer present during extrusion of the plastic tubing fromwhich the sleeve is cut than during the crimping of the ferrule on whichthe sleeve is mounted. This is done by my invention by using a solutionwhich allows a desired partial leaching out of the plasticizer. Or, ifdesired, an increase in the plasticizer can be brought about by soakingin more concentrated solution of the plasticizer.

To the same end I have found it advantageous, where the sleeves areapplied by mechanical stretching to bake them, or subject to a vacuum orother controlled treatment for evaporating a part of the plasticizerafter application to the ferrules. Using extruded tubing manufacturedfrom a plasticized copolymer of vinyl chloride and vinyl acetate whichis well known to the plastics industry, for

example, satisfactory results are attained by baking for one-half to onehour at temperatures of 375 F. to 390 F. in a closed oven. Thistreatment removes enough of the plasticizer to avoid excessive extrusionor shearing under the crimping dies, e. g., as shown in Figure 6, butnot so much as to prevent cold molding during crimping. if the sleevebecomes brittle, too much of the plasticizer has been removed.

With extruded tubing as described above, I find most advantageous forthis purpose a 5% to 10% solution of tricresyl phosphate in benzene.Depending upon the results desired, the concentration of this solutionmay be varied above 10% to about 30%, or below 5%.

The sleeve 15, when thus swollen with or without such reduction orincrease of plasticizer, shrinks firmly and strongly onto the ferrule,but retains toughness and pliability so that subsequently when theterminal is crimped onto a conductor by an ordinary crimping tool, e.g., such a one as is shown in Figure 6 and more particularly describedin the Carlson Patent No. 2,359,083, the pressure of the crimping die istransmitted evenly through the plastic to the metal.

The extent of plasticizing, degree of ploymerization and, in general,the nature of the plastic composition chosen for the insulating sleeve,should be such that its resistance to plastic flow is of the same orderas, or even less than, that of the soft copper of which the ferrule ismade, since it is essential to a good electrical connection that themetal of the ferrule should flow to some extent from under the crimpingdie. If the plastic did not yield at all it would cushion the die and sofar distribute its pressure as to impair or prevent the action on themetal ferrule required for a good connection; and on the other hand ifthe plastic flows too readily it would sofar squeeze out from under thedie as to expose the metal and thus impair its insulating function. Evenif the plastic is pressed excessively thin, however, advantage may betaken of the present'invention if the plastic is one with sufficientelastic memory so that it creeps back into the crimped areas andrestores a suflicient thicknes of insulation.

Instead of the use of a swelling liquid, I have found it advantageous,under ordinary production conditions, to use a mechanical stretching ofthe sleeve. After this stretch, the lower the temperature at which thesleeve is maintained the slower will be its recovery, whereas if thetemperature is increased the recovery is accelerated and,

by even a moderate heating, the sleeve may be brought down into grippingrelation within a very brief period. By this means again the sleeveswhich are normally smaller than the ferrule are nevertheless readilyapplied over the ferrule and then come down into strongly'grippingrelation thereon and with their ends drawn down tightly over the ends ofthe ferrule as shown in Figure 1.

The sleeves in this condition when delivered for use should be tough intheir resistance to deformation and yet substantially plastic so thatthey lend themselves well to the crimping operation and advantageouslyhave, as described above, some tendency to elastic recovery afterdeformation, which improves any condition of excessive extrusion orpuncturing if such should occur during the crimping operation.Ordinarily these properties will be developed in the plastic by removalof some 'plasticizer, e; g. by baking as described above.

When the insulated connector of Figure 1 as described above is fittedonto a wire with a bared end of the conductorin ferrule 13 and the endof the insulated portion in theprojecting end of sleeve 15, the sleeveand ferrule can be crimped into engagement with the wire and itsinsulation by ordinary commercial crimping tools, such, for example,.asthat described in the Carlson Patent No. 2,359,083, and shown in Figure6.

.Although in Figures 1 and 2 I have shown the insulating sleeve appliedto the terminal before crimping onto the*wire,.it may in some cases bemore convenient, and it is entirely feasible in accordance with myinvention, to

apply the insulating sleeve at the same time that the terminal isapplied to the wire or after the terminal is applied. To this end aterminal such as shown, for example, in Figure 3, may be applied to thebared end 2d of an insulated electrical conductor 21 and the ferrule ofthe terminal crimped to produce a secure electrical connection.Thereafter a stretched and chilled sleeve 15a is slipped over theferrule 12. overlapping slightly on the end toward the terminal portionIll and overlapping substantially at the opposite end so as to engageand secure the insulated portion of the wire 21. With the sleeve thus inplace it iswarmed to a temperature at which it tends to recover itsoriginal diameter and thus is shrunk into secure gripping relation bothto the ferrule l2 and the wire 21. Conveniently, the sleeve 15a isthreaded cold onto the wire before the terminal is applied and is slidbeyond the ferrule 12a on the insulated wire 21 until the ferrule hasbeen crimped onto the bared end of the conductor 2d. The sleeve Ilfia isthen slid back along the wire to the position shown in Figure 3, whereit is heated to shrink it onto the wire and terminal. If the terminalportion 11a is not excessively large, it is also feasible to stretch thesleeve so that it can he slipped over the terminal after application;

Because of the strength with which the shrunk tube of plastic insulationgrips the metal parts which lie within it and the partial deformationwhich causes it to engage them with a mechanical interlock, my inventionmakes possible a number of simplifications in the design of terminalsand like articles. One example of this is shown in Figure 4 wherein aterminal of utmost simplicity is made by merely bending a copper tonguelltlb of suitable shape to a right angle and either forming thereon orapplying thereto a spear 25. This spear may be of the same or a similarmetal as the tongue Titlb, advantageously integral therewith, or it maybe of a brazing or soldering alloy as more fully described in theabandoned application of Robert C. Swengel, Serial No. 517,779, filedJanuary 11, 1944.

An insulating sleeve 15b expanded and shrunk into place, in accordancewith the present invention, grips and molds itself to this terminal soas to form a ferrule securely interlocked therewith for supporting theend of an insulated wire. As suggested above, the ferrule may be appliedduring the manufacture of the terminal and the wire subsequentlyinserted into the end of the shrunk ferruleand the latter then engagedwith the wire, if desired, by a crimping or hot molding operation, orthe terminal portion canbe applied to the end of the insulated wire andthe sleeve 15!) then slipped over the end of the wire and the adjacentend of the terminal and allowed to shrink into place, engaging securelyboth the end of the terminal and the end of the wire and binding themsecurely together in conducting relation and sealing the connectionagainst corrosive influences.

The expansion of the tubes used for insulating connectors according tothe present invention can be done hydraulically by coupling one end to afluid pressure source and closing the other, or advantageously couplingit to a pressure regulating valve or other means for permitting flowunder pressure. The tube is first filled with cool or tepid water, whichexpands it to the required diameter, and then chilled, e. g. by a iiowof cold water therethrough.

This application is a division of my prior copending application SerialNo. 560,785, filed October 28, 1944-, now abandoned.

I claim:

The combination, in an electrical connector, of: a metallic conductingmember having a portion thereof adapted to be pressed into permanentcontact and engagement with an electrical conductor, and an insulatingsleeve surrounding and engaging said conducting member; said sleeve andconducting member providing an opening for reception of said conductor,said sleeve being of a tough insulating plastic material of the typewhich is moldable under pressure at room temperature whereby it ismolded by the crimping but with toughness whereby it transmits localizedcrimping pressure to produce said permanent contact and engagementwithout puncture or shearing through of the plastic material, saidsleeve being characterized by an elastic memory of a previous conditionin which its periphery was substantially less whereby it has a tendencyto shrinkage exerting a constrictive force on the connector, said sleevecontaining therein a substantial amount of vaporizable material of theclass consisting of plasticizers and solvents and swelling agents,whereby said plastic is capable of slow shrinkage during slowevaporation of said vaporizable material therefrom.

References Cited in the file of this patent UNITED STATES PATENTSWellman Oct. 9, Currie Ian. 14, Ushakofi Apr. 1, Robinson et al. July15, Grypma Mar. 17, Ushakofi Sept. 7, Watts Oct. 29, Rogoff Oct. 21,Else et al. June 22, Vickery Mar. 9,

FOREIGN PATENTS Great Britain July 12,

